This textbook chapter presents evidence of a warming climate and outlines how a clear picture of global warming has emerged since the 1980s. Students learn about sampling error sources in climate data, and compare graphical data collected by climate...(View More) scientists Jim Hansen, Philip Jones and Tom Wigley, as they follow the global warming hypothesis move through the process of science. This is the fourth chapter in the unit, Climate Change, which addresses the question of how human activities are changing Earth's climate. The resource includes three classroom investigations, links to current news articles, and a suite of pre- and post-unit assessments. A teacher's guide supports classroom use. This is chapter 4 of Climate Change, part of Global Systems Science (GSS), an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.(View Less)